1. Field of the Invention
The present invention relates to a disk friction clutch apparatus using a self-energizing effect, and more particularly, to a disk friction clutch apparatus, as a clutch apparatus disposed in a transmission of a power train used in an automobile, capable of operating a clutch with a small capacity motor only, not a hydraulic pressure, using a self-energizing effect.
2. Description of the Related Art
Clutches for automobile transmissions generally employ wet-type clutches operated in a state in which the clutches are submerged in fluid. In particular, the wet-type clutches are widely used in automatic transmissions. While the wet-type clutches have advantages of smooth gear shift and good lubrication and cooling, efficiency may decrease more or less due to power loss. As another type of clutches, a disk friction clutch including a friction disk, a pressure plate, etc., is widely applied to a manual transmission and an automated manual transmission. Such a disk friction clutch generally uses a hydraulic pressure for driving.
In recent times, in order to improve fuel efficiency, convenience, driving efficiency, etc., together with efforts to improve a conventional continuously variable transmission, development and utilization of dual clutch transmissions, in which advantages of manual and automatic transmissions are combined, and automated manual transmissions, etc., have been actively performed. While novel types of transmissions have advantages of improving fuel efficiency, a gear shift time may increase, deteriorating clutching performance and shift quality.
Methods of solving the problems may be generally classified into two types: first, development of an effective control algorithm to control a transmission, and second, improvement of a clutch mechanism.
Meanwhile, most of these novel types of transmissions use hydraulic apparatus, and only some of them use motors. When the hydraulic apparatus are used, the structure of the transmission is complicated and thus manufacturing cost also increases. The reason of using the hydraulic pressure is that a relatively large force can be generated. However, since the clutch may be operated with a small force using a self-energizing effect, the motor may be used, rather than the hydraulic apparatus.
U.S. Pat. No. 7,344,011 discloses a self-energizing clutch using inclined surfaces of wedge-shaped members to increase a clamping force of the clutch. However, the clutch may increase friction due to direct contact of surfaces thereof. U.S. Pat. No. 5,180,141 discloses a clutch driver using a ball ramp. The clutch driver has an operation ring and a control ring each of which has a groove with a circumferentially inclined surface such that balls are roll in the grooves, thereby providing a self-energizing effect. While three or four balls are required to operate the driver, the clutch may not be smoothly engaged when each ball is not in position. In addition, since the balls roll and slide on the inclined surfaces, it is difficult to ensure precise proportional control of the clamping force of the clutch.